Electro hydraulic control source for submersible vehicle

ABSTRACT

An electro hydraulic system adapted for mounting on a submersible vehicle to supply high pressure fluid flow for controlling the vehicle and various components affixed thereto. The system includes a hydraulic pump driven by a motor energized from a surface vessel, the fluid pressure at the pump output being regulated by a relief valve which has its low pressure port connected back to the return port of the pump. A preloaded sump tank coupled to the low pressure side of the relief valve operates to maintain the system fluid pressure in excess of the ambient water pressure independent of vehicle depth.

0 United States Patent 1151 3,653,403

Pettit [451 Apr. 4, 1972 [541 ELECTRO HYDRAULIC CONTROL 2,548,175 4/1951Schellinger ..60/52 B SOURCE FOR SUBMERSIBLE VEHICLE 2,872,541 2/1959Oppenheim et a1. .....60/52 B X [72] Inventor: Robert Halsey Pettit,Huntington, NY. FOREIGN PATENTS OR APPLICATIONS [73] Assignee: SperryRand Corporation 821,085 9/1959 Great Britain ..60/52 13 [22] Filed:1970 Primary Examiner-Henry T. Klinksiek [21] Appl. No.: 9,757Attorney-S. C. Yeaton [57] ABSTRACT [52] US. Cl ..137/565 511 Int. Cl..E03b 5/00 An electm hydraulic System adapted for mounting on a [58]Field 01 Search ..137/565, 569, 563, 568, 81, mersible vehicle to Supplyhigh P" fluid flow for 1 137/567 trolling the vehicle and variouscomponents affixed thereto.

The system includes a hydraulic pump driven by a motor ener- 56]References Cited gized from a surface vessel, the fluid pressure at thepump output being regulated by a relief valve which has its low pressureUNITED STATES PATENTS port connected back to the return port of thepump. A preloaded sump tank coupled to the low pressure side of therelief 2,597,050 5/1952 Audemar ..60/54.5 valve operates to maintain theSystem fluid pressure in excess 3 447,552 6/ 1969 GIOSSOn-W 1 37/81 ofthe ambient water pressure independent of vehicle depth. 3,035,5935/1962 Page 137/563 X 2,372,393 3/1945 Ray ..60/52 B 9 Claims, 2 DrawingFigures 1/ 13 24 54 42 29 3 s E R v0 23 BYPASS CH RQIEAlLIVEEF xACFTEQLED M A N F0 LD Patented April 4, 1972 v SERVO MOTOR PUMP BYPASSCHECK RELIEF 1,28, ACTUATED lg l1; VALVE VALVE VALVE F ow LL 37/ rMANIFOLD \12 43 14 31 MOTOR PUMP 71 RELIEF L54 VALVE L61 67 51 CHECK F ILTER J S VALVE 64 5 MOTOR Y Pu MP 72 73 58 S S ,fi L 1 L a I/VVE/VTO/PROBE/w H. PETT/ r ATTORNEY ELECTRO HYDRAULIC CONTROL SOURCE FOR 1SUBMERSIBLE VEHICLE BACKGROUND OF THE INVENTION -The present inventionrelates to an electro hydraulic control system particularly adapted foruse in a tethered submersible craft for providing a source of highpressure fluid to control the vehicle and various components thereon.

Submersible craft are typically controlled by means of motors connectedto the respective thrusters and other members which are required to bepowered. This approach is not suitable, however, when it is desired tominimize the size and weight of the vehicle. This is especially true inthe case of a tethered submersible vehicle incorporating severalthruster mechanisms for providing controlled motion of the vehicle withrespect to a plurality of intersecting axes. Since an individual motoris used to drive each thruster, the weight of the vehicle isproportionately increased and simultaneously its size increases as aconsequence of the need for a larger floatation assembly to support thevehicle in a neutral buoyancy condition. In addition, as the number ofdrive motors increases the power handling capacity of the tether cablemust be enlarged thereby resulting in increased cable size with theconcomitant difficulties of maneuvering of the vehicle and handling thecable upon moving the vehicle in and out of the water.

Aside from the foregoing problems other disadvantages are attendant tothe use of either do. or a.c. motors. The former, for instance, althougheasily reversible and capable of good speed control, tend to beunreliable in an underwater environment and require comparativelycomplex associated controls while the latter are characterized by poorspeed control.

In the interest of overcoming the aforementioned problems, an electrohydraulic control system is provided in accordance with the teaching ofthe present invention typically comprising only one but, if required,any larger number of electric motors mounted on the submersible craft.The motor, or motors as the case may be, operate to drive a hydraulicpump to produce a source of high pressure fluid for controlling thevehicle thruster and other movable components affixed thereto so as toenable the size and weight of both the vehicle and the tether cable tobe reduced.

SUMMARY OF THE INVENTION A preferred embodiment of an electro hydrauliccontrol system constructed according to the principles of the presentinvention comprises a fixed displacement hydraulic pump driven by an ACmotor energized through a tether cable connected to a remote generatorat a surface vessel or control station.

The return port of the pump is coupled through a low pressure line toboth the low pressure side of a relief valve and to one compartment of asump tank which includes an internal movable partition that divides thetank into two compartments. The other compartment is vented to theambient environment. In addition, the partition is pre-loaded in amanner to raise the fluid pressure in the low pressure line a prescribedamount above the ambient pressure. In this way, as the vehicle submergesto greater depths with proportionately increasing ambient pressure thefluid pressure in the low pressure line will always exceed the ambientpressure by an amount substantially equivalent to the pre-load appliedto the sump tank partition. This action furnishes pressure compensationfor the various components of the hydraulic system irrespective of thevehicle operating depth and assures that hydraulic fluid leaks from thesystem into the surrounding water rather than conversely with waterleading into the system, resulting in contamination and eventual systemfailure.

The output port of the pump is connected through a high pressure line tothe input or high pressure side of the relief valve which operates tomaintain the pressure in the high pressure line above that in the lowpressure line by an amount equal to the drop across the valve. Energydissipated in the valve in the form of heat as a consequence of itsmaintaining a constant pressure differential thereacross is readilyconducted away by the ambient water without the need for separatecooling as is customarily required in the case of such valves. Thus,high pressure flow regulated to the ambient pressure and directed fromthe motor output port back to the motor return port is provided acrossthe high and low pressure sides of the relief valve for readyapplication to external utilization devices.

A check valve, preferably connected in the high pressure line, functionsin conventional fashion to preclude fluid flow in the reverse direction,that is, to prevent high pressure fluid from being applied to the lowpressure side of the relief valve, in the event that the motorexcitation is inadvertently reversed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified schematicillustration of a preferred electro hydraulic system embodiment of theinvention,

FIG. 2 is a schematic illustration of two parallel connected motor-pumpassemblies operating in the manner of FIG. 1 for supplying high pressurefluid to the system output ports.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For simplicity of illustration,the hydraulic system is shown in schematic form apart from the vehiclein which it would normally be incorporated, it being understood that thesystem is particularly adapted for mounting on a submersible craft, ofthe type disclosed in US. Pat. application Ser. No. 9,759 filedconcurrently herewith in the name of Gerald R. Keatinge and assigned tothe assignee of the present invention, in direct exposure to the ambientwater. The system can be mounted in this manner because of the provisionof means for maintaining the fluid pressure in the system at a levelabove the ambient pressure independent of the operating depth of thevehicle as will become apparent from the following detailed description.

Referring to FIG. 1, motor 10 and pump 11 are enclosed in a housing 12forming a unitary watertight structure. Leads 13 connected to the motorare adapted for connection to a tether cable linking a submersiblecraft, on which the system is mounted, to a remote generator forenergizing the motor to drive pump 11. The return port 14 of the pump isconnected by low pressure line 16 to the system return port 17 andthrough double T coupling 18 to sump tank 19 which includes an internalmovable partition or piston 21 dividing the tank into two compartments,the upper compartment being connected to the low pressure line asindicated in the drawing. A spring 22 located in the lower compartmentpreloads the movable partition so that the pressure of the fluid in thesystem slightly exceeds the ambient pressure, typically by about 10 to20 pounds per square inch (psi). Vent 23 in the lower compartment of thesump tank is exposed to the ambient pressure which is thus able to loadpiston 21 along with the load imposed by spring 22. Hence, as thesubmersible craft descends to greater depths, the pressure in the lowercompartment increases forcing the piston upward so that the fluidpressure on the low pressure side of the hydraulic system, that is line17 and components connected thereto, always remains about 10 to 20 psiabove the ambient pressure. The volume capacity of the sump tank isderived with due consideration of compensating for system volume changes(including utilization apparatus connected to the system) caused bytemperature and pressure variations and the changing distribution of thefluid in the system resulting from operation of the various utilizationelements.

The output port 24 of pump 11 is connected by high pressure line 26 tothe system output port 27. Relief valve 28, which has its input andoutput ports 29, 31 coupled into high and low pressure lines 26, 16respectively by means of T couplings 32 and 33, operates to maintain thepressure in line 27 approximately a predetermined amount, say 1,000 psi,above that of the ambient and low pressure line 16. For example, at adepth of 1,000 feet in salt water where the pressure is about 500 psithe low pressure line is at 510 to 520 psi and the high pressure line atapproximately 1,500 psi. Thus, the hydraulic lines and all componentsneed only be designed to withstand a maximum pressure differential of1,000 psi between the internal and external pressures exerted thereon.It should be understood, of course, that the foregoing numerical valuesare illustrative only for the purpose of pointing out the depth pressurecompensation feature of the invention and that other values may be used,if desired, to satisfy particular operating requirements.

Hydraulic pump 11 is preferably of the fixed displacement type whichpumps a given volume of fluid for each revolution independent of itsrotational rate. Since the pump does not regulate the fluid pressure, arelief valve 28 is provided for this purpose. For instance, under acondition where utilization apparatus (servo actuated flow manifold andother elements not shown) connected to the system output and returnports 27, 17 are not drawing fluid, the pressure in high pressure line26 will tend to exceed the pressure in low pressure line 16 by more thanthe desired differential. This action is precluded, however, by therelief valve conducting fluid from the high pressure line to the lowpressure line to maintain the desired pressure differential. In sodoing, the relief valve dissipates energy in the form of heat which isreadily conducted away from the valve by the ambient water by virtue ofthe valve casing being directly in contact therewith. Hence, auxiliarycooling apparatus is not required. Moreover, since the product of fluidpressure and a given volume of fluid per unit time is equivalent topower it will be appreciated that the valve, in the course ofmaintaining the pressure in the high pressure line at a given level,simultaneously operates to demand constant power from the motor therebyreducing wear on the control system of the remote energizing generator.This characteristic of the system is further enhanced by presetting therelief valve for a pressure differential which corresponds to theoptimum motor load so that the motor operates continuously at maximumrated power.

in operation of the hydraulic system, high pressure fluid is selectivelyconducted to the vehicle thrusters and other tools and components on thevehicle by means of lines 30 emanating from electrically controlledservo valves incorporated in manifold 25.

A by-pass valve 34 connected across the low and high pressure lines by Tcouplings 18 and 38 is a normally open electrically operated valve whichpermits operation of the hydraulic pump without load for minimumelectrical power requirements during start up and thereafter is closedby an electrical signal transmitted through the tether cable from thesurface vessel.

Check valve 37 is connected in parallel with the by-pass and reliefvalves by means of T couplings 38 and 39 in high and low pressure lines26 and 16 respectively, the input port 41 of the check valve beingconnected to the low pressure line and its output port 42 connected tothe high pressure line. The check valve is normally closed for theproper direction of rotation of pump 11 but will open in the event thatan inadvertent phase reversal occurs in the input power causing thepumps direction of rotation to change. Thus, the check valve precludesreverse fluid flow and the resultant deleterious pressure buildup in thereturn line and at the low pressure side of the relief valve.

Finally, it should be noted that the motor and pump casing has a vent 43coupled by line 44 and T element 46 into low pressure line 16 therebyproviding depth pressure compensation for both the motor and pump. Inaddition, by using a lubricating oil as the system fluid the motor andpump are continuously lubricated for enhanced reliability.

FIG. 2 depicts two motor-pump assemblies 50, 51 of the type previouslydescribed connected in parallel for providing fluid to the system outputand return ports 52, 53. Operation of this system and its variouscomponents is the same as for the single motor-pump system of FIG. 1except for slight differences explained hereinafter. Thus. the returnports 54, 55 of the respective pumps are coupled through low pressurelines 57, 58 which connect to the system return port 53, the lowpressure (output) port 59 of the relief valve 61 and the double chambersump tank 62 as described with reference to H6. 1. Likewise, the pumpoutput ports 63, 64 are coupled through high pressure lines 66, 67 anddouble T element 68 to both the system output port 52 and the highpressure (input) port 69 of the relief valve. The check valves 71 and72, however, are not connected across the relief valve in this systembut instead are serially connected in high pressure lines 66 and 67respectively, each valve having its input port connected adjacent itsassociated pump output port and its output port connected adjacent thehigh pressure port of the relief valve. When connected in this manner,each check valve functions to preclude unintentional high pressure flowinto the output port of its associated pump. Further, under a conditionwhere one of the motors has broken down or is not energized, the relatedcheck valve will block fluid supplied by the other pump from flowinginto the output port of the non-operating pump. In each instance flowinto the output port of the pump is objectionable since such highpressure flow would eventually reach the low pressure side of the reliefvalve. The filter 73 connected in high pressure line 67 is a standardcomponent operating in conventional fashion to remove contaminants suchas dirt and wear particles from the hydraulic fluid.

Although a by-pass valve is not shown in this system one can be includedif desired. Alternatively, the function of the bypass valve can beachieved simply by actuating one of the utilization devices duringstartup of the motor. This will be apparent simply by recognizing thatthe relief valve cannot function to regulate the pressure until flowcommences, which in turn depends on pump operation. Under suchconditions, if provision was not made during motor start up forconducting flow around the hydraulic loop by some path other thanthrough the relief valve, the motor would be required to provide maximumtorque at zero speed, an undesirable condition likely to result installing.

In both of the previously described embodiments a fill valve will beneeded, of course, to remove air from the lines and thereafter fill themwith an appropriate fluid without disturbing the fixed plumbing.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes may be made withinthe purview of the appended claims without departing from the true scopeand spirit of the invention in its broader aspects.

1 claim:

1. An electro hydraulic control system for providing a source ofpressurized fluid flow in a submersible vehicle, said system havingoutput and return ports adapted for connection to external utilizationmeans and further comprising,

a hydraulic pump having output and return ports for pumping fluidcontained in said system,

a motor energizable from a remote generator for driving said pump,

high pressure fluid conductive means connecting the output port of saidpump to said system output port,

low pressure fluid conductive means connecting the return port of saidpump to said system return port,

a relief valve having its input port coupled into said high pressurefluid conductive means and its output port coupled into said lowpressure fluid conductive means for maintaining the pressure in saidhigh pressure fluid conductive means at a predetermined level in excessof the pressure in said low pressure fluid conductive means,

a sump tank having an interior movable partition for forming twodiscrete compartments in said tank, one of said compartments having avent coupled into said low pressure fluid conductive means and the otherof said compartments having a vent exposed to the ambient environment,and further including means for preloading said partition apredetermined amount in excess of the ambient pressure such that thepressure in said low pressure fluid conductive means exceeds the ambientpressure by an amount substantially equal to said preloading pressure,and check valve coupled into said system in a manner to preclude highpressure fluid from being applied to the output port of said reliefvalve under a condition of reverse operation of said motor in whichfluid is pumped out of the return port of said pump into said lowpressure fluid conductive means. 2. The apparatus of claim 1 whereinsaid check valve is serially connected in said high pressure fluidconductive means, the input port of said check valve being connectedproximate the output port of said pump and the output port of said checkvalve being connected proximate said system output port, and furtherincluding an additional pump, motor and check valve interconnected inthe manner of said pump, motor and check valve,

additional high pressure fluid conductive means connecting the outputport of said additional pump to said system output port, and

additional low pressure fluid conductive means connecting the returnport of said additional pump to said system return port.

3. The apparatus of claim 1 wherein the check valve is connected acrosssaid high and low pressure fluid conductive means with the input port ofsaid check valve connected to the low pressure conductive means.

4. The apparatus of claim 1 further including a by-pass valve connectedacross the output and return ports of said pump, said by-pass valvebeing normally open during startup of said motor for minimum loading atthat time and thereafter actuated to a closed position in normaloperation of said electro hydraulic system.

5 The apparatus of claim 1 wherein said pump is of the fixeddisplacement type which pumps a given volume of fluid for each periodiccycle of operation thereby enabling said relief valve to be preset foroperation of said motor at maximum power rating.

6. The apparatus of claim 1 wherein said motor and said pump areenclosed in a unitary watertight casing having a vent coupled to saidlow pressure fluid conductive means thereby providing depth pressurecompensation for said motor and said pump.

7. The apparatus of claim 6 wherein said fluid is a lubricating medium.

8. The apparatus of claim 6 wherein said pump is of the fixeddisplacement type which pumps a given volume of fluid for each periodiccycle of operation thereby enabling said relief valve to be preset foroperation of said motor at maximum power rating.

9. The apparatus of claim 8 wherein said preloading means comprises aspring positioned in the ambient exposed compartment of said sump tankfor forcing said partition against the fluid in the other compartment ofsaid tank, and further including a filter connected in said highpressure fluid conductive means for removing contaminant particles fromsaid fluid.

1. An electro hydraulic control system for providing a source ofpressurized fluid flow in a submersible vehicle, said system havingoutput and return ports adapted for connection to external utilizationmeans and further comprising, a hydraulic pump having output and returnports for pumping fluid contained in said system, a motor energizablefrom a remote generator for driving said pump, high pressure fluidconductive means connecting the output port of said pump to said systemoutput port, low pressure fluid conductive means connecting the returnport of said pump to said system return port, a relief valve having itsinput port coupled into said high pressure fluid conductive means andits output port coupled into said low pressure fluid conductive meansfor maintaining the pressure in said high pressure fluid conductivemeans at a predetermined level in excess of the pressure in said lowpressure fluid conductive means, a sump tank having an interior movablepartition for forming two discrete compartments in said tank, one ofsaid compartments having a vent coupled into said low pressure fluidconductive means and the other of said compartments having a ventexposed to the ambient environment, and further including means forpreloading said partition a predetermined amount in excess of theambient pressure such that the pressure in said low pressure fluidconductive means exceeds the ambient pressure by an amount substantiallyequal to said preloading pressure, and a check valve coupled into saidsystem in a manner to preclude high pressure fluid from being applied tothe output port of said relief valve under a condition of reverseoperation of said motor in which fluid is pumped out of the return portof said pump into said low pressure fluid conductive means.
 2. Theapparatus of claim 1 wherein said check valve is serially connected insaid high pressure fluid conductive means, the input port of said checkvalve being connected proximate the output port of said pump and theoutput port of said check valve being connected proximate said systemoutput port, and further including an additional pump, motor and checkvalve interconnected in the manner of said pump, motor and check valve,additional high pressure fluid conductive means connecting the outputport of said additional pump to said system output port, and additionallow pressure fluid conductive means connecting the return port of saidadditional pump to said system return port.
 3. The apparatus of claim 1wherein the check valve is connected across said high and low pressurefluid conductive means with the input port of said check valve connectedto the low pressure conductive means.
 4. The apparatus of claim 1further including a by-pass valve connected across the output and returnports of said pump, said by-pass valve being normally open duringstartup of said motor for minimum loading at that time and thereafteractuated to a closed position in normal operation of said electrohydraulic system.
 5. The apparatus of claim 1 wherein said pump is ofthe fixed displacement type which pumps a given volume of fluid for eachperiodic cycle of operation thereby enabling said relief valve to bepreset for operation of said motor at maximum power rating.
 6. Theapparatus of claim 1 wherein said motor and said pump are enclosed in aunitary watertight casing having a vent coupled to said low pressurefluid conductive means thereby providing depth pressure compensation forsaid motor and said pump.
 7. The apparatus of claim 6 wherein said fluidis a lubricating medium.
 8. The apparatus of claim 6 wherein said pumpis of the fixed displacement type which pumps a given volume of fluidfor each periodic cycle of operation thereby enabling said relief valveto be preset for operation of said motor at maximum power rating.
 9. Theapparatus of claim 8 wherein said preloading means comprises a springpositioned in the ambient exposed compartment of said sump tank forforcing said partition against the fluid in the other compartment ofsaid tank, and further including a filter connected in said highpressure fluid conductive means for removing contaminant particles fromsaid fluid.